There is a paradox in being asked to talk about breach of contract in the Unidroit Principles for International Commercial Contracts, since the Principles do not anywhere contain the words "breach of contract". At first sight this would be surprising, at least to most common lawyers, since both the concept and terminology of breach figure largely in their discussions. It is not of course that the Principles envisage that all contracts which are subject to the Principles will be perfectly performed! Rather, the Principles have chosen to talk of performance and non-performance. Non-performance, however, is not the same as breach since it may be excused. Breach of contract, in the common law sense, is non-excused non-performance within the Principles. Non-performance may be excused for two different kinds of reasons. One group of reasons consists of unexpected external events outside the control of the non-performing party. In other words, force majeure for a civil lawyer and the doctrines of impossibility of performance and frustration for a common lawyer. These are covered by article 7.1.6, which is discussed in more detail by Dietrich Maskow in another paper. It is important to point out, however, that while Englisih textbook writers have traditionally treated frustration as an event terminating contracts, the Principles treat force majeure as an excuse for non-performance. Termination may follow, but this would be because of a choice by the other party. Of course, as was pointed out by Nicholas some years ago, English law has in fact always recognized implicitly that there are situations where unexpected events excuse non-performance but do not bring the contract to an end.' Non-performance may also be excused by reason of the conduct of the other party. Article 7.1.2 contains two different sets of excuses. The first is the conduct of the other party. An interesting example which was given during the discussion is that of the seller who is unable to deliver goods to the buyer because the buyer does not open his factory to receive the goods at the agreed time. Probably most systems would concur in the result that the buyer cannot